The invention relates to a housing enclosing the impeller of a propeller pump, having a gap ring disposed within the housing.
The split ring disposed in the housing or a housing part of a propeller pump serves to lessen the wear produced on the outside diameter of the propeller by gap cavitation. Furthermore, such gap rings are used wherever dirty liquids with high material ablation rates must be dealt with. Thus, the gap rings composed of a cavitation- and wear-resistant material serve to increase the useful life of the pump housing. This is utilized chiefly in constantly running propeller pumps and with aggressive liquids and liquid which carry a large percentage of dirt.
The gap ring, which heretofore has been in the form of a continuous, annular piece, serves to counteract any enlargement of the radial gap between the propeller and the surrounding pump housing and the reduction of the pump output caused thereby. In the case of liquids containing fibrous components, a stripping or cutting edge is disposed on the gap ring to prevent clogging. For this purpose a longitudinal slot is disposed on the inside of the gap ring, which incidentally makes it necessary to increase the wall thickness. The cost producing a gap ring of the kind described is relatively high, since its outside diameter has to be precisely matched to the housing in which it is contained.